The present invention relates generally to a heat exchanger comprising substantially rectangular plates in alignment with one another and provided by embossing with a head-like profile of uniform total depth. The plates are alternatingly rotated by 180.degree. relative to one another, with a peripheral gasket between them, and are fastened detachably into a stack with the facing profiles of adjacent plates resting on one another. The plates include portions in which are formed first and second flow spaces, encompassed by the peripheral gasket, for a first medium flowing in one direction and a second medium flowing in the opposite direction, respectively, the first and the second flow portions being disposed diagonally opposite one another and being guided substantially parallel to one another, and the flow spaces are supplied with the respective medium via inlet and outlet openings in alignment with one another and formed by holes disposed in the corner regions of the plates. The plates also have a middle, rectangular heat exchange zone and two triangular heat exchange zones adjoining the middle zone on opposite sides, and the triangular zones carry the flow cross section of the middle zone to that of the inlet and outlet opening. For this purpose, the profile of the triangular zones comprises substantially divergent ray-like passages originating at the respective opening and merging into a chevron-like array of flow passages having a common pitch defining a mutual spacing.
In known heat exchangers of this type, the relatively thin-walled plates, which are often also identical in shape to one another, are held together in a frame and fastened between thicker end plates into a stack; the end plates contain the connections for the media, which are guided along the plate stack via channels that are formed by the aforementioned openings in the plates, in combination with a suitable embodiment of the gaskets.
In the flow spaces between the plates, depending on the embodiment of the plate embossing, the flow is either diagonal or substantially parallel to the longitudinal direction of the plates, and correspondingly there are either diagonally opposed holes in the plates, or openings located to one side of the vertical center of the plates, that serve as inlet and outlet openings.
In the case of the above-mentioned triangular zones of the plates, the profile is embodied, in known instances, in the form of beads having a mutual spacing from one another, which originating at the plate opening associated with them extend substantially in ray-like form and as a rule form an angle on the order of 25.degree. to 40.degree. with the vertical line of symmetry of the plates. Since adjoining plates are rotated by 180.degree. relative to one another, the profiles of the triangular zones of adjoining plates intersect, as a result of which the plates here abut one another at the intersecting points.
The known embodiment, in this form, of the triangular zones of the plates has the disadvantage, however, that it results in a relatively high pressure loss, and with that loss, the most uniform possible distribution of the respective medium over the entire triangular surface area is virtually unattainable or is at least much more difficult, because in terms of the flow paths formed between the individual beads, an exchange of pressure and media is virtually impossible on the way between the associated plate opening and the rectangular zone of the heat exchange surface. As a result, the distribution of media over the triangular zones is so impaired that these zones can participate in the task of heat exchange only to a secondary extent.